1. Field of the Invention
This invention concerns a heater or heat exchanger for heating particulate material and particularly suited for use in a sintering process.
2. Description of Related Art
Metallic parts can be fabricated using, for example, a sintering process. Powdered metal is packed or consolidated into a mold and then pressure and/or heat is applied, thereby causing the particles of metal powder to fuse together. It has been found that the consolidation step is facilitated if the particulate material is pre-heated prior to sintering.
A common pre-heating process involves transporting the metal powder through a heated tube, using an auger or a heated auger which revolves within the tube. The revolving auger causes the metal powder to tumble within the heated tube, thereby picking up heat from the tube, as the auger advances the powder toward an output end of the tube.
However, a problem with this heating process is that the powder does not heat uniformly, tends to "cake" or lump together. It is also found that the caking limits the maximum temperature to which the powder can be heated.
Various types of heating devices are shown in U.S. Pat. Nos. 2,917,284, 3,255,814, 3,831,665, 4,051,590, 4,153,485, 4,276,020, 4,469,925, 5,169,572, 5,213,816, and 5,401,937. Some or all of these devices suffer in that they are relatively complex or complicated in design and may not uniformly heat the particulate material as desired.
What is needed, therefore, is a device which is simple in design and construction which will be relatively inexpensive to manufacture, or produce; and which will improve the heating of materials passing therethrough.